"It's unreal," the official said of Cantor's loss to his underdog Tea Party-backed challenger David Brat.

Their shock hasn't stopped liberals from rejoicing over the defeat of a man who earned the nickname "Dr. No" for his vigorous opposition to the Democratic agenda in Congress. The official who spoke with Business Insider described Cantor's loss as being a "rebuke" of the GOP "on every level."

"Eric Cantor is the member of the House leadership that's tasked with putting out their legislative agenda," the official said.

Because of this, the official predicted Cantor's lost would have left other Republicans terrified.

"I guarantee every single Republican Senate and gubernatorial candidate that has a primary left – and that's a lot of them – their consultants and staff are doing emergency conference calls and hyperventilating into paper bags right now," said the official.

The official also said Cantor's shocking shellacking proved Republican operatives have flawed "strategy" and "tactics."

"Their pollsters had put out stuff that they were 34 points up," the official said of Cantor's campaign. "They're just so out of tune with what the lay of the land is."

According to the official, internal polls released by Team Cantor that showed him ahead were "totally bogus." While they allowed for the possibility Cantor's campaign actually believed his numbers, they noted Cantor recently tempered his support for immigration reform as a potential sign he may have known he was vulnerable to Brat's challenge from his right flank. The official also pointed to the fact Cantor spent hundreds of thousands of dollars more than Brat on the race.

"Maybe they did see this coming," said the official. "He poured so much money in."

Because of this, the official speculated the release of internal data that allegedly showed Cantor with a wide lead may have been designed "just to spin reporters."

"Republicans have kind of a track record of putting out bad polls," said the official.

Brat's victory puts him on a course to face Democrat John "Jack" Trammell in the general election. Trammell's website notes he is "in part" named for former President John F. Kennedy and declares his intention to fight "extremism and 'business as usual' in Washington." Both Brat and Trammell are professors at Randolph-Macon College in Ashland, Virginia.

With Cantor unable to run on the Republican Party line, the Democratic Party official said there are "a couple scenarios" for what might happen next. They suggested some of these possibilities "could put the seat in play" for Trammell, however, they cautioned, "It's obviously very early."

The official noted Cantor might run as a write-in candidate, which could result in a situation where the conservative vote "gets split" and creates an opening for Trammell. Cantor's campaign did not respond to a request from Business Insider shortly after his loss.

Describing the district as one that merely "leans Republican" and isn't overwhelmingly conservative, the official also suggested Brat might simply lose to Trammell outright.

"You have a guy that is so far to the right, this guy is areal loon from everything I've seen," the official said of Brat. "That's not the district this is. This is a suburban Virginia district, it's not a Glenn Beck crowd."

Trammell did not respond to multiple requests for comment from Business Insider. However, the Virginia Democratic Party released a statement on his behalf wherein he said he is expecting a "spirited campaign."

"I am honored and humbled to accept the Democratic nomination in Virginia’s 7th Congressional District. I am running because I believe Virginians are hungry for a radical change from the dysfunctional and reckless politics being practiced by those in Congress – and the results of tonight’s primary election are the proof," Trammell said. "In the coming months, I look forward to a spirited campaign where can talk about the issues that matter to our community, and how we can get Congress re-focused on the priorities that truly matter to us."

"Eric Cantor has been defeated in the Republican Primary in the 7th Congressional District!" the post said. "Democrats now have a chance to win this district with Jack Trammell for Congress! Go Trammell!"